Air pressure — Science definition

Defined in 2 courses:

Where it is taught

In use

Fronts don't wander on their own — they're steered by patterns of air pressure, the weight of the atmosphere pressing down on a given spot, which we measure with a barometer.

Air Masses, Fronts & Pressure

Questions using air pressure

Problem 1

Which statement correctly uses air pressure in Air, Pressure & Uneven Heating?
  1. One illustrative result establishes every real condition and needs no further evidence.
  2. Air has no mass because it is invisible.
  3. Uneven heating determines every wind direction without other influences.
  4. air pressure: Force per area associated with air’s interactions and atmospheric conditions.
Answer and explanation

air pressure: Force per area associated with air’s interactions and atmospheric conditions.

Force per area associated with air’s interactions and atmospheric conditions. The difference is 12 hPa. The simplified model predicts air responding from A toward lower-pressure B. This is not an exact real-wind forecast, because the actual path also depends on rotation, friction, terrain, and surrounding pressure patterns. Pressure is a comparison, not a cause inferred from one unlabeled arrow.

Problem 2

Standard sea-level air pressure is about 1013 millibars. A barometer reading of 998 millibars most likely signals...
  1. A low-pressure system, with cloudier, stormier weather ahead
  2. A high-pressure system, with clear, calm weather ahead
  3. No change in the weather at all
  4. A broken barometer
Answer and explanation

A low-pressure system, with cloudier, stormier weather ahead

A reading well below the roughly 1013-millibar average indicates lower-than-average pressure, which is associated with rising air and increasing clouds or storms.

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